In various types of rotating machinery, it has historically been a problem to provide bearings and bushings which do not fail. A bearing is defined as a machine part in which another part turns or slies. A bearing is subjected to compressional forces, pressures, or thrusts, and must be capable of withstanding a specified weight when a structure such as a shaft, rests upon such bearing. The generally accepted definition of thrust, is the rearward force exerted endwise or in an axial direction through a propeller shaft, to give forward motion.
Referring to FIG. 1, a conventional double thrust bearing is illustrated. This conventional double thrust bearing includes two {2} rows of ball bearings enclosed in a housing. These bearings have been met with high failure rates because of excessive thrust loads and inadequate lubrication. Moreover, these thrust bearings require shutdown every two weeks for lubrication. Experience has shown that the failure rates of machines having such thrust bearings were extremely high, approximately 66 percent per year, causing extensive maintenance costs and loss of production.
Referring to FIG. 2, in an attempt to solve the above problems, a second generation thrust bearing was developed by Assignee. The tapered thrust bearing of FIG. 2, includes an inner and outer race a and b both made of steel, with rollers c therebetween. Such design also includes a brass shim d and a spacer sleeve e also made of steel. This design reduced the failure rate to about 25% per year.
It is therefore an object of this invention to provide a bearing which is self-aligning and provides minimal friction between itself and a rotating surface.
It is also an object of this invention to provide a bearing and bearing assembly which is efficient not only in terms of capabilities, but also in terms of drastic reduction in down time of expensive machinery used in complex processes.
We have now found that the objects of this invention can be achieved by providing an improved bearing and bearing assembly, which can substantially withstand severe compressional or thrust forces.
Despite the significant advances offered by Assignee's second generation of tapered thrust bearings, there remains a need for improved thrust bearings and assemblies having an improved life expectancy, low failure rate, can be easily fabricated, and requires less frequent lubrication.